The applicant claims and requests a foreign priority, through the Paris Convention for the Protection of Industry Property, based on a patent application filed in the Republic of Korea (South Korea) with the filing date of Nov. 7, 2000, with the patent application number 2000-0065949, by the applicant.
1. Field of the Invention
The present invention relates to a radio frequency coil for a magnetic resonance image apparatus being a medical diagnostic apparatus for grasping the internal structure of a specimen such as a patient, and more particularly, to a radio frequency coil for a magnetic resonance image apparatus which can adjust a gap between support frames for supporting a specimen according to the physical structure of the specimen.
2. Description of the Related Art
There are an X-ray CT (Computer Tomography) using an X-ray and a MRI (Magnetic Resonance Image) using a magnetic signal of an element in a human body as tomographies for grasping the internal structure of a human body. A tomography using a magnetic resonance phenomenon has some advantages in comparison with a tomography of an X-ray CT. The tomography using a magnetic resonance phenomenon uses a magnetic field which does no harm to a human body, which is thus not harmful even in the case of long-time and frequent tomographic diagnosis, and can discriminate particles which has not been discriminated in the case of an X-ray tomography. Also, the magnetic resonance tomography can obtain a two-dimensional or three-dimensional tomographic image in any direction of X-, Y- and Z-axis (or any three-dimensional direction) and at any position. With the above-described merits, the MRI equipment has become an essential medical image apparatus.
The MRI equipment includes a main magnet, a coil and a scan processor. The main magnet is a permanent magnet, an electromagnet or a superconductive magnet using a superconductor, in order to form a strong magnetic filed, in which the intensity of the magnetic filed ranges from 0.2 Tesla to 7.0 Tesla. Here, one Tesla is a magnetic filed of ten thousand gauss. The coil includes a slant magnetic coil for forming a slant magnetic filed of X-, Y- and Z-axis directions, a transmission radio frequency (RF) coil for giving energy to an atomic nucleus spin in a human body of a patient and forming a magnetic resonance signal and a reception radio frequency (RF) coil for receiving the magnetic resonance signal emitted from the human body which is a specimen. The scan processor includes a spectrometer for demodulating the received magnetic resonance signal and amplifying it, a controller for controlling operation of each coil, and a processor for performing a Fourier transform operation in order to transform the received signal into data on the XY plane.
An example of a magnetic resonance image apparatus having the above-described elements is shown in FIG. 1, which has a structure that a three-turn coil 2 is disposed on a cylindrical support frame 1 with an equal interval, in which a specimen 3 is inserted into the cylindrical support frame 1.
In a conventional magnetic resonance image apparatus, the cylindrical support frame 1 has a closed structure. As a result, a patient is easy to feel impatience during a photographic action of a tomography and a rejection against the magnetic resonance image apparatus. Further, since the cylindrical support frame has a predetermined limited space, it is difficult to perform an accurate tomography in the case that a patient is tall or small in a physical size. That is, in the case that a physical size of a patient is large, equipment of a variety of sizes is needed according to the size of the patient. In the case that a physical size of a patient is small, a quality of an image is lowered since a patient is distant from the magnetic resonance image apparatus and it takes much time to take a photograph since a patient moves frequently.
To solve the above problems, it is an object of the present invention to provide a radio frequency coil for a magnetic resonance image apparatus, for solving a rejection against a magnetic resonance image apparatus by reducing impatience of a patient during photography, adjusting a gap between a patient and a magnetic resonance image apparatus according to the size of a patient, receiving a signal having a less loss by facilitating a close contact between the patient and the magnetic resonance image apparatus, to thereby obtain an enhanced image, and shortening a photographic time efficiently by minimizing movement of the patient through a close contact of the patient.
To accomplish the above object of the present invention, there is provided a radio frequency coil for a magnetic resonance image apparatus comprising: a first support frame provided with a first coil; a second support frame opposing the first support frame and provided with a second coil; a gap adjuster for adjusting a gap between the first and second support frames according to the size of a specimen; and a frequency sustainer for sustaining a resonance frequency set according to change of the gap in the gap adjuster.
Preferably, the first support frame is fixedly installed on a base and the second support frame is slidably installed on the base. Preferably, the gap adjuster comprises: a pair of first guide bars fixedly installed on the lower portion of the first support frame with a predetermined distance from each other, and formed in the lengthy direction of the second support frame; a second guide bar fixedly installed on the lower portion of the second support frame and combined between the pair of the first guide bars slidably; and a first guide rail provided on the base, for guiding the second support frame.
The frequency sustainer comprises: a first cylindrical electrode electrically connected to the first coil, fixed on the first support frame, and formed in the lengthy direction of the gap adjustment, in which an opening is formed in an outer circumferential surface so that a surface area increases gradually; and a second cylindrical electrode electrically connected to the second coil, fixed to the second support frame, and combined with the first coil slidably in which an insulator is interposed between the first cylindrical electrode and the second cylindrical electrode, to thereby increase or decrease capacitance values of the first and second cylindrical electrodes according to adjustment of the gap between the first and second support frames when reactance values of the first and second coils increase or decrease.
The radio frequency coil for a magnetic resonance image apparatus can adjust a gap according to the physical size of a patient since the gap between the first and second support frames can be adjusted.